Formulations containing polysiloxanes have been topically applied to tissue products in order to increase the softness of the product. In particular, adding silicone compositions to a facial tissue can impart improved softness to the tissue while maintaining the tissue's strength. For example, polysiloxane treated tissues are described in U.S. Pat. Nos. 4,950,545; 5,227,242; 5,558,873; 6,054,020; 6,231,719 and 6,432,270. A variety of substituted and non-substituted polysiloxanes can be used.
While polysiloxanes are exceptionally good at improving softness, there can be disadvantages in their use. Polysiloxanes are generally hydrophobic meaning they tend to repel water. Tissue products treated with polysiloxane can be less absorbent than tissue products not containing polysiloxane. The tissue's absorbency can be further reduced by using amino-functional polysiloxanes, which tend to be more hydrophobic in nature. Increased hydrophobicity in a paper product, such as a tissue, can adversely impact the ability of the paper product to absorb liquids. Hydrophobic agents can also prevent bath tissue from becoming quickly saturated and disintegrating or dispersing when disposed of in a toilet creating problems when flushing the tissue.
Increasing the hydrophobicity of a paper product can provide various advantages. By making tissue paper hydrophobic, the fluid strike-through properties of the tissue can be improved. For example, fluids absorbed by the tissue can remain within the interior of the tissue paper and not be transferred through to the other side to wet a person's hands while using the tissue. Other methods to increase the barrier properties of tissue, such as adding sizing agents to the tissue product, can be used.
In order to increase the tissue absorbency, the hydrophobic additives can be topically applied in discrete locations on a tissue product leaving relatively large untreated areas of the product such that less than about 50 percent of the surface of the product is covered with the additive. The discrete placement of the additive on the tissue product can provide regions of hydrophobicity and hydrophilicity. The discrete placement may require a majority of the tissue's surface to not contain the additive. As a result, reduced product benefits, such as softness, are realized relative to a product having a high level of surface coverage. In addition to reduced softness benefits, such products may not achieve the desirable balance of rapid initial intake and increased strike through time. U.S. patent application Ser. No. 10/289,557, entitled Soft Tissue Hydrophilic Tissue Products Containing Polysiloxane and Having Unique Absorbent Properties, filed on Nov. 6, 2002, and herein incorporated by reference, describes the application of a surfactant in a patterned arrangement to enhance the absorbent properties of a hydrophobic tissue product to balance the strikethrough and absorbent rate.
As seen, there is an ongoing need to develop tissue products that have good hand protection properties yet meet the criteria for absorbency generally demanded in dry tissue products. There is also a need to manufacture these products with technologies currently available and that introduce a minimum incremental cost to the product.